Queues and other buffering means are often employed in network devices to compensate for the transmission differential between the incoming packet rate and the outgoing packet rate. To prevent the overflow and/or underflow of the queue, various active queue management mechanisms may be employed. The basic idea behind active queue management mechanisms such as, for example, random early detection (RED), is to detect incipient congestion early and to convey congestion notification to the end-systems, allowing them to reduce their transmission rates before queue overflow and sustained packet loss occur.
In the basic RED scheme, as well as in improvements thereto such as described in the above-referenced related U.S. patent application Ser. No. 09/455,445, filed Dec. 6, 1999, a queue length average is maintained and used, along with a number of queue thresholds, to detect congestion. If congestion is detected, incoming packets are dropped (or marked, e.g., see S. Floyd, “TCP and Explicit Congestion Notification”, ACM Computer Communication Review, Vol. 24, No. 5, October 1994, pp. 10-23) in a random probabilistic manner where the probability is a function of recent buffer fill history.
Despite the benefits associated with the above-described basic and improved RED schemes, there are still shortcomings associated therewith. One such shortcoming is that conventional RED-based mechanisms typically require tuning of various control parameters such as, for example, the queue threshold settings and the maximum drop probability. These tuning procedures usually are ad hoc or based on heuristics and, as such, often do not provide for optimal queue management. Moreover, conventional RED-based mechanisms generally do not stabilize the queue size and thus result in unpredictable results. Thus, there remains a need for enhancing the effectiveness of a RED-based mechanism by providing a systematic process for determining optimal settings for one or more control parameters of the RED-based mechanism to provide for stable and predictable results.